Abbas al-Omran told FNA that al-Khawaja's blood pressure has increased, he has lost over 25 kilos of weight and his vital signs show critical conditions.
Al-Khawaja was given a life sentence after he was arrested because of participating in a peaceful rally in Bahrain. He went on hunger-strike over 60 days ago.
Al-Omran voiced concern about al-Khawaja's critical health conditions, and said the al-Khalifa regime has transferred him to a military hospital and refrains from sending him to a civilian medical center fearing people's access to him.
Al-Khawaja was arrested in April of last year for his role in the anti-government demonstrations that swept through his country in February and March.
In June, al-Khawaja and seven other Shiite opposition activists were found guilty of plotting to overthrow the country's royal family. They were sentenced to life in prison.
The Bahrain Center for Human Rights, a nonprofit human rights group started by Abdulhadi al-Khawaja and for which his daughter works, has appealed for his immediate release on humanitarian grounds.
His life is now in serious danger, Maryam al-Khawaja, his daughter, said last month, "and getting to a situation where there might be an irreparable damage to his physical well-being, if he survives."
Maryam al-Khawaja said 13 prominent leaders had their case taken to the Court of Cassation Monday, where lawyers requested that they be released pending a court decision.
The judge refused the request, and announced that the decision will be read on April 23, she said.
"We urge the government to take into consideration the deteriorating health condition of Abdulhadi Al-Khawaja that cannot wait until the court's decision," she said.
"Any damage to the health of Abdulhadi Al-Khawaja is the responsibility of the Bahraini government, including keeping him alive."
The government in Bahrain has not yet responded to requests for comment.
Rights group Amnesty International also has called for al-Khawaja's immediate and unconditional release.
Phillip Luther, its Middle East and North Africa director, said in a statement, "The Bahraini authorities have made pledges that they would release people who were imprisoned for exercising their right to freedom of expression, but the continued imprisonment of Abdulhadi al-Khawaja demonstrates that they are not serious about fulfilling such promises."
The rights group considers al-Khawaja a "prisoner of conscience, detained solely for exercising his right to freedom of expression," and says he began his hunger strike in February to protest his sentence.
In March, the United Nations issued a statement expressing concern about "the health of human rights defenders who are on hunger strike in protest against their imprisonment for participating in last year's mass demonstrations."
Another right group, the Human Rights Watch (HRW), also filed a critical report earlier this month, which said Bahrain had not lived up to its commitments on reform.
Anti-government protesters have been holding peaceful demonstrations across Bahrain since mid-February 2011, calling for an end to the Al Khalifa dynasty's over-40-year rule.
Violence against the defenseless people escalated after a Saudi-led conglomerate of police, security and military forces from the Persian Gulf Cooperation Council (PGCC) member states - Saudi Arabia, Kuwait, the United Arab Emirates, Oman and Qatar - were dispatched to the tiny Persian Gulf kingdom on March 13, 2011, to help Manama crack down on peaceful protestors.
So far, tens of people have been killed, hundreds have gone missing and thousands of others have been injured.